For many applications it is desirable to utilize couplings consisting of a male coupling member (nipple) attached to one end of a fluid conduit line and a female coupling member (coupler) attached to an end of an opposing fluid conduit line such that the opposing male and female members may be readily joined together by a simple axial movement of the male nipple into the female coupler. One of the earliest types of these couplings is shown in U.S. Pat. No. 2,966,371. A spring-biased valve on the male coupling member in this patent has a conical head that engages a corresponding conical head of a spring-biased valve on the female coupling member when the coupling members are moved together, causing the valves to move away from respective valve seats and open a flow path through the conduit lines. The valve in the female coupler is retained within a spring-biased, axially-slideable cylindrical sleeve, which includes an annular front surface that mates flush against an annular front surface of the body of the male nipple when the two coupling members are connected together.
For quick disconnect-type couplings, the female coupling member typically has an outer axially slideable release/locking collar or sleeve that controls radial movement of detent/locking balls from a radially outward position when the collar is retracted, to a radially inward position when the collar is urged to its forward position. When the detent balls are in their radially outward position, the male coupling member is free to be readily inserted into or removed from the female coupler, while when the detent balls are in their radially inward position, they engage and retain the male coupling member in the female coupling member.
An example of a prior art fluid coupling utilizing detent balls and a locking collar may be had by reference to U.S. Pat. No. 3,464,436, owned by the assignee of the present application and incorporated herein by reference. Since at least 1988, the assignee of the present invention has also manufactured NS and FF Series Quick Disconnect Couplings through its Quick Coupling Division in Minneapolis, Minn. that included such balls and collars. Reference is also made to International Standard ISO 7241-1 entitled "Hydraulic Fluid power-quick acting couplings" issued by the International Organization for Standardization, First Edition 1987-04-01, Part 1 which sets forth dimensions and requirements for such quick-acting couplings.
For many industrial fluid flow applications, it is desirable that there be a minimal amount of fluid loss and a minimal amount of air inclusion when the male nipple is coupled to or uncoupled from the female coupler. One type of prior art coupling having a push-to-connect feature that provides minimal fluid loss is shown in U.S. Pat. No. 4,181,150, also owned by the assignee of the present application and incorporated herein by reference. In this coupling, a spring-biased ball check valve in the male coupling member is received within a conical seat in a spring-biased valve in the female coupling member. The ball check valve substantially fills the conical space in the valve of the female portion to minimize spills and air inclusion.
While this type of coupling has received wide-spread acceptance in the marketplace, there are some male nipples in commercial use that are not easily and/or fully compatible with the female coupler shown in the '150 patent. These male nipples include a conical valve head extending beyond the body portion of the nipple such as that shown in the above-mentioned International Standard ISO 7241-1. These valve heads would not mate fully with the wider and shallower conical seat for the ball check valve shown in U.S. Pat. No. 4,181,150.
It is known that certain low-spill, quick-disconnect type couplings have been developed to accept such male nipples with conical heads. German reference DE 3904098 A1 for example, shows a low-spill, quick-disconnect type coupling that includes a male coupling member having a conical valve head. The female half of this coupling includes a spring-biased stem valve having a conical opening with a recess that closely receives the valve head of the male half. An annular front surface on the spring-biased sleeve surrounding the conical valve of the female half mates flush against an annular front surface on the body of the male half prior to the valves moving away from their respective valve seats. This close cooperation between the coupling members prevents spills and air inclusion during the connection and disconnection of the coupling halves. U.S. Pat. No. 5,709,243 shows an essentially identical coupling where the conical head of the valve of the male half is received in a conical recess in the stem valve of the female half, with a spring-biased sleeve surrounding the female stem valve.
The stem valve in the female half of DE 3904098 A1 extends rearwardly, away from the male half, and is fixed via radial links to the female valve body. It is also known to allow the stem valve to move axially rearward a selected amount during connection, and then bottom against a stop to then cause the valves halves to move away from their respective valve seats. This is shown, for example, in German reference DE 4114480 A1 (FIG. 6); German reference DE 8809220.8; U.S. Pat. No. 2,966,371; and U.S. Pat. No. 4,098,292. U.S. Pat. No. 5,709,243 also shows this structure.
While the above couplings have female couplers which allow quick-disconnect for male nipples with conical valve heads, it is necessary to overcome the system pressure applied against the valve sleeve when inserting the male nipple into the female coupler. In addition, high system pressure in the female half can cause leakage between the body and sleeve, and between the sleeve and stem valve after disconnect, which can require high pressure seals and special retainers in some applications. This can limit the usefulness of the couplers, and can add to the material, assembly and maintenance costs.
Thus, it is believed there is a demand in the industry for a further improved low spill, quick-disconnect coupling, and particularly an improved female coupler which can accept male coupling members having valves with conical heads, where the coupling has i) a low coupling force to allow easy connect of the male and female coupling members, and ii) where the female coupler can withstand higher system pressures without leakage or damage to the coupler.